Forms based auth has been one of those features I've had difficulty getting to work smoothly, especially in a hosted environment. Harder still is making it work with an Active Directory membership provider instead of a database. Why would you want to do this anyway? It looks prettier.

A side note also, one of the things I noticed about the above documentation : While very thorough it tells you how rather than why to take certain paths. For instance a web application is extended rather than using the default zone – why? Setting the default zone to FBA would mean search would be unable to connect and through a plethora of fairly vague messages in the event logs. Etc.